DE 28 49 700 A1, DE 33 33 604 A1, DE 43 35 199 C1 or DE 10 2006 017 774 A1 describe height adjustable vehicle seats with level control. There is provided in each case for the level control a control circuit which comprises the seat frame, the pneumatic spring and the control device including a sensing member, sliding control member and valve device. If the actual value of the height, which is established, for example, as the differential angle between the cranks, differs from the desired value, generally owing to a deflection of the seat frame, the pneumatic spring is controlled in such a manner that it acts counter to the deflection, and the actual value again reaches the desired value. For the height adjustment, the desired value is modified in accordance with the height which is to be newly adjusted, so that the level control treats the current actual value as a deviation from the desired value and moves the seat frame to the desired new height. In the case of technical implementation, known vehicle seats have a partially complex structure. In addition, an increase in the precision of the level control and the height adjustment would also be desirable.
DE 103 54 635 B4 proposes a vehicle seat of the type mentioned in the introduction, in which the precision of the establishment of the actual value is increased by using a cable roll with a cable (in place of measuring the angle between the cranks). The position of the cable roll is magnetically detected and electrically evaluated, which makes the solution costly.